This invention relates to a novel method of distinguishing lubricants utilized in compressors. Lubricants have been used in compressors generally to protect the frictionally engaged components therein from wear. More particularly, this invention relates to a simple yet accurate method of distinguishing between an alkylbenzene and a naphthenic lubricant which are widely used as lubricants in compressors. Thus, for example, lubricants have been used in conjunction with refrigerants in compressors of mobile refrigeration systems. Earlier on naphthenic oil, such as Suniso 3GS was widely used. Lately, an alkylbenzene such as Zerol-150 (Shrieve Chemicals) has been used exclusively. Chemically, the naphthenic oils are completely saturated hydrocarbons consisting of cyclic structures e.g. cycloparaffinic molecules. Alkylbenzenes contain aromatic rings with branched hydrocarbons having a general formula as shown in FIG. 1: ##STR1## in which n is a positive integer.
They are prepared for example by the known Friedel-Crafts reaction such as by alkylation of benzene with alkylchlorides or olefins.
Commercial manufacturers of refrigeration systems such as Thermo King has used alkylbenzenes as a lubricant in combination with fluorocarbon refrigerants available under the tradename R-12, R-22, R-500 and R-502 within the last decade. However, it is estimated that there are about a half-million refrigeration systems currently in use which have utilized both types of lubricants.
There is no easy and quick method of distinguishing which of these two lubricants are used in the system. The present practice is to withdraw a lubricant sample from the compressor and bring it to the laboratory for analysis. Most common method presently used to distinguish these two types of compounds relies on a spectroscopic technique (infra-red spectrophotometer) which gives distinct absorption peaks due to aromatic benzene at 1600 cm.sup.1 in alkylbenzene lubricants.
With the recent legislative changes, which prohibits the use of high Ozone Depletion Potential (ODP) and high Global Warming Potential (GWP) refrigerants, refrigerants such as R-12 which is dichloro difluoro methane has to be replaced by compounds such as MP-66 which is a ternary blend of chloro difluoro methane, difluoro ethane and tetrafluoro ethane or R-134a which is tetrafluoro ethane. It has been concluded that while R-134a will be suitable for new compressors, it may not be economically feasible to retrofit the existing compressors with R-134a, because of certain compatibility problems. Refrigerant MP-66 has been suggested as a suitable replacement of R-12 in existing compressors. The lubricant of choice with MP-66 is alkylbenzene. Therefore, it is important for manufacturers of refrigeration systems to find out the type of oil in the existing compressors. The primary reasons to learn the identity of the lubricant are:
a. Savings--if the existing lubricant turns out to be alkylbenzene, then one needs to replace only R-12 refrigerant with MP-66, without changing the lubricant. PA1 b. If the lubricant is a naphthenic oil, then one would need to replace both the refrigerant and lubricant with MP-66 and alkylbenzene to avoid any compatibility problems.